Is there any rules to specify private ip address

I guess 192.168., 169, 10* are all private ips, but I am not sure. Anyone can point out?


Take a look at RFC5735 for a complete list of reserved networks. You're looking for "Private-Use Networks".

Address Block       Present Use                Reference
------------------------------------------------------------------          Private-Use Networks       RFC 1918       Private-Use Networks       RFC 1918      Private-Use Networks       RFC 1918
  • I thought 169.254 should also be
    – user705414
    Oct 18 '11 at 23:28
  • @user705414, from RFC5735: - This is the "link local" block. As described in RFC3927, it is allocated for communication between hosts on a single link. Hosts obtain these addresses by auto-configuration, such as when a DHCP server cannot be found.
    – rid
    Oct 18 '11 at 23:39

Private IPs are IP addresses in the subnets reserved for private addresses:


All other (non-reserved) IP addresses can (and most likely do) refer to actual computers in the public internet, so they should not be used in private networks.

  • Yeah, I guess as a practice one should never use public IP even in private networks. I will edit my answer. Oct 19 '11 at 4:48

If you are using it in a network that wont connect to outside, it is fine. Else, you can consider using NAT translations. Use the range provided for private IP addresses, as given in some of the answers.

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